Syntheses of Ag/Cu alloy and Ag/Cu alloy core Cu shell nanoparticles using a polyol method

Abstract

Ag–Cu bimetallic nanoparticles were prepared by reducing mixtures of AgNO3 and Cu(OAc)2·H2O in ethylene glycol (EG) in the presence of poly(vinylpyrrolidone) (PVP) at 175 °C for 5–60 min. At high [Ag]/[Cu] molar ratios of 1 and 2 or at a short reaction time below 5 min, Ag rich Ag/Cu alloy particles were formed. On the other hand, at low [Ag]/[Cu] molar ratios of 0.25 and 0.5 or a long reaction time above ≈15 min, Cu shells were overgrown on Au/Cu cores and new Ag/Cu alloy core Cu shell nanoparticles, denoted as Ag/Cu@Cu, were produced. The formation of Ag/Cu and Ag/Cu@Cu particles was examined using energy dispersed X-ray spectroscopic (EDS) measurements. The growth mechanisms of Ag/Cu and Ag/Cu@Cu particles are discussed on the basis of TEM-EDS and ultraviolet (UV)-visible (Vis)-near infrared (NIR) extinction spectral data. The time dependence of UV-Vis spectra indicated that the Cu component of Ag/Cu@Cu particles has higher antioxidized property than that of Cu and Cu@Ag particles.